Many propulsion and transmission systems are known in the prior art for use with bicycles and other manually-powered cycles. Most commonly, the cycle is propelled by foot pedals which are connected through suitable transmission means to one or more of the cycle wheels, the pedals locating about a central axis passing through the cycle frame and moving along a circular path of movement about the axis when pumped by the rider.
One of the problems with the conventional pedalling arrangement just described is that of inefficient and uneven distribution of torque force applied to the pedals. It will be appreciated that maximum force from the pedal to the wheel being driven occurs when the crank arm to which the pedal is attached is essentially horizontal. Power applied to the cycle transmission is at its lowest value when the crank arm supporting the pedal is at or near vertical. Also, of course, the force applied to the transmission of the cycle continuously varies as the pedal traverses its circular path between the crank arm vertical and horizontal positions. This fluctuation of torque force applied to the cycle drive wheel substantially reduces the overall efficiency of the manually powered cycle drive.
Applicant is aware of the following United States patents: U.S. Pat. Nos. 602,230, issued Apr. 12, 1898, 3,66,1,404, issued May 9, 1972, and 4,019,230, issued Apr. 26, 1977, all of which relate to propelling mechanisms for manually powered bicycles.
U.S. Pat. No. 602,230 discloses a propelling mechanism wherein the pedals are connected to crank arms which rotate about a common pivot. The pedals essentially move in circular paths of movement, although some variance or deviation from these strictly circular paths results from the fact that the pedals can slide axially relative to the crank arms. The pedals do not traverse a complete circle but rather a segment thereof. The crank arms alternately pivotally move up and down relative to the central axis and operate a ratchet mechanism which drives the drive wheel of the bicycle.
U.S. Pat. No. 3,661,404 also teaches the idea of employing alternating-motion pedals, the movement of which is converted by a particular chain means into a rotating motion which is applied to the driving wheel of the bicycle. The two pedals of the bicycle are mounted on the free ends of two control levers arranged on either side of a frame, each lever pivoting about a substantially horizontal first shaft attached to the rear bicycle fork in parallel relationship to and adjacent to the driving wheel axle. Each lever is hung from one free end of a drive chain cooperating with two free-wheeling pinions mounted on a second shaft of the bicycle frame.
U.S. Pat. No. 4,019,230 discloses a reciprocating powered bicycle wherein pedals move along a path comprising a segment of a circle, the pedals being connected to crank arms rotating about a common axis through the bicycle frame. The pedals drive the bicycle drive chain through a roller clutch and ratchet arrangement. A rocker arm connected to the pedal crank arms operates to pull one pedal up as the other pedal is depressed by the rider.